Internal combustion engine with a coolant loop

ABSTRACT

In an internal combustion engine including a coolant loop for cooling a component of the engine, and a thermostatic valve for controlling the coolant flow in said loop, a temperature control device is provided which comprises a purely mechanical temperature sensor disposed in intimate heat transfer relationship with the component, and mechanical means extend between the temperature sensor and the thermostatic valve and define a path for transmitting temperature-related information from the former to the latter.

This is a Continuation-in-Part application of International Application PCT/EP03/11520 filed Oct. 17, 2003 and claiming priority of German application 102 52 154.9 filed Nov. 9, 2002.

BACKGROUND OF THE INVENTION

The invention relates to an internal combustion engine including a coolant loop for cooling a component or an operating medium of the engine, a thermostatic valve for controlling the flow of coolant in said cooling loop, and a temperature control device for controlling the temperature of the engine component or operating medium.

DE 23 47 038 A1 discloses an internal combustion engine including a cooling loop and a preferably wax-filled temperature sensor which may be disposed within the coolant loop and can be used to control the temperature of, for example, a cylinder head of the engine as a function of the coolant temperature.

With this kind of control, the engine component, such as the cylinder head, is usually cooled too much, especially during operation in the partial-load range. As a result, it takes the engine much longer to reach its optimal operating temperature so that it cannot run optimally for a relatively long time. Moreover, such overcooling of the cylinder head can cause internal stresses to be set up therein which may result in structural damage to the cylinder head.

Another drawback of conventional internal combustion engines resides in that they require a continuous control flow since, without it, the temperature sensor disposed in the coolant receives no information and, hence, cannot properly function. However, a continuous control flow, i.e. flow of coolant, can result in an overcooling of the engine component.

Temperature control devices of this kind can also be used to control the temperature of operating mediums, such as motor oil, transmission fluid and fuel. In controlling the cooling of such operating mediums, conventional control devices depend also on the temperature of the coolant and, therefore, tend to initiate cooling of the operating medium long before it has reached its maximum permissible temperature limit. Such an unnecessary overcooling of the operating medium will not allow an optimal temperature control of the operating medium to be achieved. The above-mentioned problem arising due to the need of a control flow is present also in cooling the operating mediums of the engine.

These problems have been known in the art. Thus, DE 41 13 294 C1 discloses a temperature sensor for use in the cylinder head of an internal combustion engine which senses the temperature of a component of the cylinder head and sends its temperature reading to an engine control unit, which controls the operation of a thermostatic valve in the cooling circuit.

Such temperature control devices are complicated and expensive and, therefore, find only limited use in the mass production of internal combustion engines. What particularly adds to their cost is their need for an actuator controlled by the engine control unit.

The invention has for its principal objective to solve these problems by providing an internal combustion engine with an improved and simple device for controlling the temperature of a component and/or operating medium of the engine in a more effective way.

SUMMARY OF THE INVENTION

In an internal combustion engine including a coolant loop for cooling a component of the engine, and a thermostatic valve for controlling the coolant flow in said loop, a temperature control device is provided which comprises a purely mechanical temperature sensor disposed in intimate heat transfer relationship with the component, and mechanical means extend between the temperature sensor and the thermostatic valve and define a path for transmitting temperature-related information from the former to the latter.

The invention accordingly resides in the provision of an internal combustion including a coolant loop for cooling a component or operating medium of the engine, a thermostatic valve for controlling the coolant flow in the coolant loop, and a temperature sensor for controlling the temperature of said engine component or operating medium. The temperature control device comprises a purely mechanical temperature sensor disposed in intimate heat transfer relationship with the engine component or operating medium, and mechanical means connecting the temperature sensor to the thermostatic valve and forming a path for transmitting temperature-related information from the temperature sensor to the thermostatic valve.

By positioning the temperature sensor, which acts as a remote sensor, such that it is in direct and intimate heat transfer relationship with the component whose temperature is to be controlled, the controlled quantity, i.e. the degree to which the thermostatic valve opens, is dependent directly on the regulating quantity, i.e. the temperature of the engine component, so that cooling can be achieved depending on load and on the temperature of the engine component or operating medium, thus resulting in a much more direct temperature control than can be achieved with conventional controls. Such direct temperature control makes it possible for the engine component or operating medium to be cooled more effectively than before under full-load conditions so that the engine requires less cooling under partial-load conditions. This leads, under partial-load conditions, to a temperature increase of the component or operating medium which, in turn, allows the engine to operate more efficiently. Furthermore, the temperature control device embodying the invention also simplifies, or even renders redundant, the processes currently used to calculate the exact quantity of coolant to be supplied to engine components or operating mediums.

In addition, the temperature control device embodying the invention does not require a control flow since its temperature sensor takes the needed information directly from the engine component and requires no temperature information concerning the coolant. This eliminates the common heat-loss problem previously encountered, especially in cooling operating mediums, so that the internal combustion engine can warm up more quickly.

All of these improvements are obtained at a very low cost since the temperature control device embodying the invention does not need any expensive electronic elements. The invention attains its objective by providing an improved temperature control device utilizing a mechanical temperature sensor and mechanical means connecting it to a thermostatic valve. The temperature control device according to the invention is particularly suitable for use in the cylinder head of an internal combustion engine or for controlling the temperature of a winding of the generator connected to the engine. A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of an internal combustion engine embodying the invention, and FIG. 2 is an enlarged view of one of various temperatures sensors shown in FIG. 1.

The internal combustion engine schematically shown in FIG. 1 includes a crankcase 2 containing a predetermined quantity of motor oil 4, a cylinder head 3 mounted on the crankcase 2, a gear unit 5 adjoining the crankcase 2 and containing transmission oil, and a fuel tank 7 containing fuel 8 for powering the engine 1. As an alternative, the motor oil 4 and the transmission oil 6 could be combined in one volume.

The internal combustion engine 1 includes further a temperature control device 9 which in this case is used to control the temperature of a component of the engine, i.e. the cylinder head 3, and to control the temperature of several operating mediums, i.e. the engine oil 4, the transmission oil 6, and the fuel 8. Of course, it could also be used for controlling the temperature of, for example, only one engine component and/or one operating medium or of several engine components and one or more operating mediums.

In the embodiment shown in FIG. 1, the temperature control device 9 comprises four temperature sensors 10, 11, 12 and 13 disposed directly within the cylinder head 3, the motor oil 4, the transmission oil 6 and the fuel 8, respectively. In accordance with the invention, these temperature sensors are purely mechanical and require no electrical power supply. One of them will be more fully described later herein with particular reference to FIG. 2.

As shown in FIG. 1, the temperature sensor 10 disposed within the cylinder head 3 communicates through a purely mechanical connecting line 14 with a thermostatic valve 15 in the cooling circuit 16 of the internal combustion engine 1. The thermostatic valve 10 controls the operation of a coolant pump 17 which serves to pump coolant also through the cylinder head 3. The cooling circuit 16 includes further a water cooler 18, an exhaust return cooler 19, a heater 20, and an auxiliary heater. Reference to the four last-mentioned components 18, 19, 20 and 21 is made only for the sake of completeness.

The cooling circuit 16 includes a branch loop 22 including an oil cooler 23 for the motor oil 4 and for the transmission oil 6, a heat exchanger 24 for the fuel 8, and a water cooler 25 for supplying the heat exchanger 24 with coolant. The two temperature sensors 11 and 12 communicate with a thermostatic valve 28 through mechanical connections 26 and 27, respectively. The temperature sensor 13 communicates with a thermostatic valve 30 via a mechanical connection 29. Both thermostatic valves 28 and 30 are part of a branch loop 22. Of course, it would also be possible to provide separate thermostatic valves for the two temperature sensors 11 and 12, and/or to cool the motor oil 4 and the transmission oil 6 in separate coolers.

Although the temperature control device 9 of the illustrated embodiment utilizes four temperature sensors 10, 11, 12 and 13 and three thermostatic valves 15, 28, 30, it should be understood that, depending on the intended use, it could have any number of such temperature sensors and thermostatic valves.

Each temperature sensor 10, 11, 12 or 13 transmits the temperature information obtained from the associated engine component directly to the associated thermostatic valve 15, 28 or 30 through a path formed by the associated mechanical connection 14, 26, 27 or 29. In response, the thermostatic valve will change its valve nozzle area in direct relation to the transmitted temperature information such that an increase of the temperature of the engine component will immediately result in an increased coolant flow through the valve.

For instance, a temperature increase detected by the temperature sensor 10 in the cylinder head 3 will immediately result in a stronger coolant flow through the cylinder head 3; and a temperature increase detected by the temperature sensor 11 or 12 will immediately result in an increased coolant flow through the oil cooler 23 or heat exchanger 24, respectively. Thus, there is a direct connection between the temperature of the engine component and to the cooling thereof. In other words, a temperature increase of the engine component will result in an almost instant increase in the cooling thereof which allows the respective thermostatic valves 15, 28, 30 to open only at relatively high temperatures. This allows the cylinder head 3 to be kept at a higher temperature closer to the permissible limit and thereby creates more favorable operating conditions for the engine, and protects the operating mediums, i.e. the motor oil, transmission oil and fuel 8, at low temperatures from being unnecessarily cooled since the temperature sensors 10, 11, 12 and 13 do not need any control flow and, therefore, will not initiate a response causing coolant to flow through the oil cooler 23 and the heat exchanger 24.

Referring now to FIG. 2 which is an enlarged, representation showing one of the temperature sensors 10, 11, 12, 13, the sensor comprises a tubular member 31 which is open on one side and disposed within the engine component, i.e. the cylinder head 3, or in one of the operating mediums, i.e. the motor oil 4, transmission fluid and/or the fuel 31, Disposed within the tubular member is an expansion element 32 containing or consisting of an expansion material, such as wax, which will expand when its temperature rises above a predetermined degree. Based upon its operating characteristics, the tubular member 31 may be referred to as a capillary tube. As apparent from FIG. 2, expansion material is disposed also within the mechanical connection line 14, 26, 27, 29. When the expansion element 32 expands, the resultant pressure increase in the connection line 14, 26, 27, 29 determines when and how wide the associated thermostatic valve 15, 28, 30 will open.

Although not shown herein, it will be understood that the temperature control device 9 can also be used to control the winding temperature of the generator utilized by and forming a component of the internal combustion engine 1. 

1. An internal combustion engine including a coolant loop for cooling a component of said engine, a thermostatic valve for controlling the coolant flow in said loop, and a temperature control device for controlling the temperature of said engine component, said temperature control device comprising a purely mechanical temperature sensor disposed in intimate heat transfer relationship with said engine component, and mechanical means connecting said temperature sensor to said thermostatic valve and forming a path for transmitting temperature-related information from the temperature sensor to the thermostatic valve.
 2. An internal combustion engine according to claim 1, wherein said mechanical means comprises a tube.
 3. An internal combustion engine according to claim 2, wherein said tube has a temperature-responsive expansion material disposed therein.
 4. An internal combustion engine according to claim 2, wherein said temperature sensor comprises a tubular member disposed in physical contact with said engine component, and a temperature-responsive expansion element disposed in said tubular member.
 5. An internal combustion engine according to claim 4, wherein said expansion element comprises wax.
 6. An internal combustion engine according to claim 1, wherein said engine component is a cylinder head, said temperature sensor being disposed within said cylinder head.
 7. An internal combustion engine according to claim 1, wherein said engine component is a generator having a winding, said temperature sensor being disposed within said winding. 